Picor Corporation • picorpower.com

PI2161-EVAL1 User Guide Rev. 1.0

current is sourced from the power supply and

its output voltage will drop, but when the

MOSFET disconnects the load (shorted) from

the source, the bench power supply may

produce high output voltage with high current

capability that may damage the device under

test.

If a bench power supply has to be used, or there

is some wiring inter connection between PI2161-

EVAL1 input (Vin+ and Vin-) and the power

source, add a large electrolytic capacitor

between Vin+ and Vin- terminals to reduce

power source high voltage transient after load

disconnect.

6.2. Place the scope probes very close to PI2161 D

pin and SH pin to measure Vout and Vin, and

make sure that the scope ground leads are very

short.

6.3. Current trip point:

To find the exact current trip level, repeat steps

5.1 to 5.9 and then increment the load current

slowly.

The current can be monitored by a

current probe placed at the unit input or by

reading the current display at the power supply

(PS1) or at the electronic load display.

The

actual trip current is the current right before the

PI2161 turns the output off, VO output will go to

0V to indicate that the output is disconnect from

the source.

After PI2161 turns the output off by pulling the

MOSFET gate low, it will hold the MOSFET in an

off condition until it is reset.

6.4. Device Reset:

To reset PI2161 after a fault (high load current),

recycle PI2161

by sliding SW1 knob to Off

position and then slide the knob back to On

position.

6.5. Output short test

Enable PS1 and then apply a short at the load

(Vout). The short can be applied electronically

using the electronic load, a MOSFET connected

between Vout+ and Vout- or simply by connecting

Vout+ to Vout-. Then measure the response time

between when the output current reached the

set trip point and when PI2161 disconnect the

load. An example for PI2161 response time to an

output short circuit is shown in Figure 5.

Figure 5: Plot of PI2161 response time to a forward over-current condition

94.4ns

Set Trip Current

at 10.5A

(Rs=200m

Ω)

Input Current (5A/div)

Output Voltage [SH] (5V/div)

PG pin (5V/div)

Input Voltage [D] (5V/div)

Start Turn

off & latch

MOSFET

Avalanche

At 69V

120.4ns

Output Voltage [SH] (5V/div)

Input Current (5A/div)

Input Voltage [D] (5V/div)

PG pin (5V/div)

Turn off

& latch

Test Setup:

DUT: PI2161-EVAL1

Vin = 45V

Output Load = 1.5A

Rs (R1) = 200mΩ

First applied slow ramping load

current and determined the trip

current: 10.5A

Test: Apply output short

PI2161 was enabled and load

current is at 1.5A, then shorted

Vout+ to Vout- with a MOSFET.

The current ramped at 230A/μs.

PI2161 turned the output off at

load current of 33A, by pulling

the MOSFET gate low and latch

it low.

PI2161 internal MOSFET starts to

turn off 94ns after the current

reach the trip point (10.5A). And

current reached 0A within 120ns.